Elementary school-age students who participated in an after-school program with plenty of physical activity showed greater improvements in several areas of so-called "executive function" than similar students who did not participate.

Executive function refers to a range of mental or "cognitive" skills that include memory, focus, attention and the ability to switch back and forth between tasks.

Lead researcher Charles Hillman said that students who had the highest attendance in the program saw the biggest gains in mental skills.

"I think these are the hardest evidence we have available that time spent in physical activities, which would include physical education and recess, not only doesn't detract from academic goals, but it might enhance academic performance," said Hillman, a professor of kinesiology and community health at the University of Illinois at Urbana-Champaign.

The findings were published online Sept. 29 and in the October print issue of the journal Pediatrics.

The researchers randomly assigned 221 children, aged 7 to 9, to either the after-school program or a wait-list for the program. The after-school program occurred for nearly all of the school year (150 days). Over two hours, physical activity alternated with rest periods, resulting in about 70 minutes of moderate to vigorous exercise every weekday, Hillman said.

The children took tests to measure their "inhibition" and their "cognitive flexibility," which is basically their ability to switch between different tasks successfully, such as reading something and then answering questions about that reading, Hillman said.

Inhibition involves two types of thinking skills, Hillman explained: the ability to ignore distractions in the environment to focus on something specific, and the ability to stop a well-learned response quickly when necessary.

If a child automatically starts to ride his bicycle across a street when a light turns green, for example, a strong inhibition response refers to how quickly he can prevent himself from going forward when he notices a car running the red light.

Although children in both the after-school program and the wait-list group experienced improvements in physical fitness, inhibition and cognitive flexibility, the after-school program participants made bigger gains in all three areas.

The program participants also showed improvements in attention that were not seen in the wait-list group, and they had smaller gains in body mass index (BMI) than the wait-list students. BMI is a measurement of body fat based on height and weight.

Because the study directly compared two similar groups of children, the findings support the idea that the physical activity actually caused the brain improvements, though it's less clear how physical activity improves thinking skills, the experts said.

"From a brain structure perspective, we know that regions of the brain gain volume with fitness intervention from studies with older adults," Hillman said, though that does not mean increased volume leads to better thinking.

Meanwhile, other studies have found changes in the way neurotransmitters work in the brain after physical activity, and how exercise affects the hippocampus, the part of the brain responsible for memory and learning, he said.

Most likely, Hillman said, several different mechanisms are at work in the brain that allow physical activity to improve mental abilities.
The study was well-designed, according to an expert who was familiar with the findings.

Nathaniel Riggs, an associate professor of human development and family studies at Colorado State University in Fort Collins, said, "One important direction for future research is to actually measure physiological processes that may be able to explain these associations."

Riggs pointed out that the study even compared the results of children in different groups who had been matched in terms of age, sex, race/ethnicity and socioeconomic status. One of the only weaknesses of the study is the inability to know how long the mental gains from the exercise might last, he said.

But executive control -- the collection of mental skills that got a boost from the exercise -- is critical for positive development, Riggs added.

"It's actually more strongly correlated with academic achievement than is IQ," he said. "The policy implication is that schools will want to consider providing increased opportunities for physical activity to their students not only to promote better health, but also to potentially increase academic achievement."

The benefits could extend even beyond academic success, Riggs said.

"Executive control is also associated with fewer conduct problems, which can interfere with classroom instruction, less drug use, which interferes with learning, and less risky sexual behavior, which can result in school drop-out due to unintended pregnancies," he said.

The study was funded by the U.S. National Institute of Child Health and Human Development and the National Institutes of Health.